Flow Rate Measurement

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In this project we learnt about flow measurement devices.

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Flow Rate Measurement

  1. 1. Flow Rate Measurement Group Member Registration Number M e h r o z e A l i N a j m i ME-113071 M u h a m m a d Ta h a ME-113085 R a s i k h Ta r i q ME-113006 M u h a m m a d A d a m K h a n ME-113125 M u h a m m a d M u b b a s h a r K h a n ME-113126 Instrumentation and Measurement Project Presentation – ME Department, Mohammad Ali Jinnah University, Islamabad. 1
  2. 2. Presentation Flow Introduction Flow Meters Calibration of Flow Meter Project Accomplishments M.A. Jinnah University, Flow Rate Measuring Instruments 2
  3. 3. Mehroze Ali Najmi ME 113071 3
  4. 4. Introduction To Fluids 4
  5. 5. Introduction To Fluids  A fluid is anything that flows, usually a liquid or a gas.  Fluids are treated as continuous media.  Their motion and state can be specified in terms of the velocity u, pressure p, density ρ , etc.  Ability of fluid to change at every point in space x and at time t.  Depending on the relationship between shear stress, and the rate of strain and its derivatives, fluids can be categorize as: 1. Newtonian fluid 2. Non-Newtonian fluid
  6. 6. Newtonian Fluids  Fluids for which the shearing stress is linearly related to the rate of shearing strain are called or known as Newtonian fluid and also referred as rate of angular deformation.  Fortunately most common fluids, both liquids and gases, are Newtonian.
  7. 7. Non-Newtonian Fluids: • Fluids for which the shearing stress is not linearly related to the rate of shearing strain are called or known as non-Newtonian fluids. • The slope of the shearing stress versus rate of shearing strain graph is called apparent viscosity. • Denoted by (µap ). • For Newtonian fluids the apparent viscosity is the same as the viscosity and is independent of shear rate. • On the basis of this apparent viscosity we have two more types of Non- Newtonian Fluids: 1. shear thinning fluids 2. shear thickening fluids
  8. 8. Shear Thinning Fluids • For shear thinning fluids the apparent viscosity decreases with increasing shear rate. • The harder the fluid is sheared, the less viscous it becomes. Many colloidal suspensions and polymer solutions are shear thinning • Example: Paint does not drip from the brush because the shear rate is small and the apparent viscosity is large.
  9. 9. Shear Thickening Fluids • For shear thickening fluids the apparent viscosity increases with increasing shear rate. • The harder the fluid is sheared, the more viscous it become. • Example: Common examples of this type of fluid include water–corn starch mixture and water–sand mixture . • Water sand is known as “quicksand”.
  10. 10. Variation of shearing stress with rate of shearing strain for several types of fluids, including common non-Newtonian fluids
  11. 11. Volumetric Flow Rate • Volume flow rate is the volume of a fluid which passes through a given surface area in time t. • The SI unit of volumetric flow rate is m3/s. • There are many types of instruments for measuring liquid and/or gas flow. • The accuracy of flow measurement will vary from instrument to instrument and the desired accuracy will vary from application to application. • Measuring flow is one of the most important aspects of process control. • Flow tends to be the most difficult variable to measure.
  12. 12. Properties Affecting Fluid Flow • Velocity of Fluid: Velocity of fluid is defined as the fluid speed in the direction of flow. Fluid velocity depends on the head pressure that is forcing the fluid through the pipe. Greater the head pressures, faster the fluid flow rate. • Pipe Size: Increasing the diameter and/or length of the pipe will increase the potential of flow. • Pipe Friction: Pipe Friction reduces the flow rate through the pipe. Flow rate of the fluid is slower near walls of the pipe than at the center.
  13. 13. Properties Affecting Fluid Flow • Fluid Viscosity: Viscosity is physical resistance to flow. Higher viscosity the fluid, the slower fluid flow. • Specific Gravity of the Fluid: At any given operating condition, higher the fluid's specific gravity, lower the fluid's flow rate. • Fluid Condition: The condition of the fluid (clean or dirty) also limitations in flow measurement, some measuring devices become blocked/plugged or eroded if dirty fluids are used.
  14. 14. Properties Affecting Fluid Flow • Velocity Profiles: Velocity profiles have major effect on the accuracy and performance of most flow meters. The shape of the velocity profile inside a pipe depends on the momentum or internal forces of the fluid, that moves the fluid through the pipe, the viscous forces of the fluid that tend to slow the fluid as passes near the pipe walls.
  15. 15. Types of Flow Profiles: There are three types of flow based on the profile. 1. Laminar or Streamlined Flow 2. Transitional flow 3. Turbulent flow • Laminar or Streamlined Flow: Laminar flow is described as liquid flowing through a pipeline, divisible into layers moving parallel to each other.
  16. 16. Types of Flow Profiles • Transitional flow: Transitional flow is between laminar and turbulent flow profiles. Its behavior is difficult to predict and it may oscillate between the laminar and turbulent flow profiles. • Turbulent flow: Turbulent is the most common type of flow pattern found in pipes. Turbulent flow is the flow pattern which has a transverse velocity (swirls, eddy current).
  17. 17. Figure 1: Laminar, Transition and Turbulent Flow Types
  18. 18. Muhammad Taha ME 113085
  19. 19. Importance of Fluid Measurement • The most diverse substances are transported and distributed in piping system in every single day • The fluids flowing through pipe have different properties, so different flow measuring devices are used • The maintenance of definite rates of flow is important for maximum efficiency and production
  20. 20. • Costs which are based on flow measurements will be incorrect if the measurement are erroneous • Huge volumes of gas, steam and liquid may have to be measured daily, a very small percentage error can amount to large sums. Importance of Fluid Measurement
  21. 21. Types of Flow Meters Generally 5 Types of flow meters are used: 1. Mechanical Flow Meters 2. Electronic Flow Meters 3. Differential pressure Flow Meters 4. Variable area Flow Meters 5. Mass Flow Meters
  22. 22. Types of Flow Meters 1.Mechanical flow meters • Mechanical flow meters that measure flow using an arrangement of moving parts, either by passing isolated known volumes of a fluid through a series of gears or chambers or by means of a spinning turbine or rotor
  23. 23. Types of Flow Meters 1.Mechanical flow meters  Turbine Flow Meter • The Turbine Flow meter translates the mechanical action of the turbine rotating in the liquid flow around an axis into user-readable rate of flow.
  24. 24. Types of Flow Meters 1.Mechanical flow meters  Turbine Flow Meter • When fluid hits the blade of turbine it starts rotating and it creates a pulse (frequency) • This rotation is sensed and output is given in frequency.
  25. 25. Types of Flow Meters 1.Mechanical flow meters  Turbine Flow Meter • When fluid moves faster more pulses are generated • This frequency is transformed to an electric signal using Voltage Transducer, which can be integrated with a software e.g. ( LABVIEW) • Thus calibrated into a readable output for flow rate
  26. 26. Types of Flow Meters 2) Electronic flow meters • Electronic flow meters represent a logical grouping of flow measurement technologies. All have no moving parts and are made possible by today's sophisticated electronics technology
  27. 27. Types of flow meters 2) Electronic flow meters • Many types of electronic flow meters are used:  Magnetic flow meters,  Vortex flow meters,  Ultrasonic flow meters
  28. 28. Rasikh Tariq ME 113006 28
  29. 29. Outline 29 Flow Rate Measuring Instruments Differential Pressure Flow Rate Measurement Types Orifice Meter Venturi Meter Nozzle Meter Measurement System Installation Advantages Disadvantages Mass Flow Meters
  30. 30. Differential Pressure Flow Rate Measurement Principal → Change in velocity of fluid yields a change in pressure Applicability for Best Possible Results → Flow conditions are turbulent 30
  31. 31. Orifice Meter Governing Principal →Bernoulli's Equation C = Orifice Flow Coefficient 31
  32. 32. Venturi Meter Governing Principal →Bernoulli's Equation 32
  33. 33. Nozzle Meter  The ISA 1932 nozzle  The long radius nozzle  The venturi nozzle 33
  34. 34. Applicability of Nozzle Meters • The flow nozzle is recommended for both clean and dirty liquids. • The range ability is 4 to 1. • The relative pressure loss is medium. • Typical accuracy is 1-2% of full range. • Required upstream pipe length is 10 to 30 diameters. • The viscosity effect high. 34
  35. 35. Measurement System 35 Static Pressure Profile Pressure Loss Transmitter P diaphragm Remote Flow Indicator or Controller Output of the transmitter is not linear. Thus, signal conditioning is necessary.
  36. 36. Installation 36
  37. 37. Comparison 37 Advantages Disadvantages  They are easy to install.  One differential pressure transmitter applies for any pipe size.  Many DP sensing materials are available to meet process requirements.  Orifice plates have no moving parts and have been researched extensively; therefore, application data well documented.  The process fluid is in the impulse lines to the differential transmitter may freeze or block.  Their accuracy is affected by changes in density, viscosity, and temperature.  They require frequent calibration.
  38. 38. 38 The flow meter accelerates, linearizes and stabilizes the velocity profile. (Source: Veris Inc)
  39. 39. Outline Flow Rate Measuring Instruments Differential Pressure Flow Rate Measurement Types Orifice Meter Venturi Meter Nozzle Meter Measurement System Installation Advantages Disadvantages Mass Flow Meters 39
  40. 40. Muhammad Adam Khan ME 113125 40
  41. 41. Variable Area Flow Meters • Fluid flow moves the float upward against gravity. • Float will find equilibrium when area around float generates enough drag equal to weight - buoyancy. • Some types have a guide rod to keep float stable. • Low Cost (pricing usually starts < $50) • Simple Reliable Design • Can Measure Liquid or Gas Flows • Tolerates Dirty Liquids or Solids in Liquid 42
  42. 42. Measurement Procedure 1. For accurate flow measurement, the system media, pressure, and temperature should be consistent with the calibration of the flowmeter. 2. Close the integral metering valve on the flowmeter before the system is pressurized. 3. Open the shutoff valves upstream and downstream of the flowmeter 4. Add system pressure slowly. 5. Adjust the metering valve until the flowmeter shows the desired flow rate. 43
  43. 43. Installation  flush out the pipe or tube leading to the flow meter.  For gas flow applications, dry the pipe or tube leading to the flow meter  The variable area flow meter must be installed as vertically as possible to ensure the most accurate flow reading  Direction of flow is from bottom to top in vertical models and can be either right to left or left to right in horizontal models, as specified when ordering.  Align the pipe or tube leading to and from the flow meter axially with the connections on the flow meter to keep them free of stress. If necessary, support the pipe or tube leading to and from the flow meter to prevent vibration being transmitted to the flow meter. 44
  44. 44. Measuring Principles of Variable Area Flowmeters • Flow Rate Analysis. • The forces acting on the bob lead to equilibrium between: • the weight of the bob bgVb acting downwards • the buoyancy force gVb and • the drag force Fd acting upwards.  Where Vb is the volume and  rb is the density of the bob,  r is the density of the fluid, and  g is the gravitational acceleration dbbb FgVgV
  45. 45. where the parameter is defined in terms of a constant K =Vb/D3 b characteristic of the shape of the bob: for turbulent flow: for laminar flow:
  46. 46. Similarity Analysis • The basic scaling parameter for flow is the Reynolds number, defined as: •where UIN is the velocity at the rotameter inlet, and the tube diameter D is represented by its value at the inlet, equal to the bob diameter Db. • Through the Reynolds number regimes of laminar or turbulent flow, and particularly important for the rotameter flow regimes with strong or weak viscosity dependence can be distinguished. •It has been found to be practical for rotameters to use an alternative characteristic number, the Ruppel number, defined as:
  47. 47. where mb = bD3 b is the mass of the bob. By combining Equations, the mass flow through the rotameter can be written as: The relationship between the Ruppel number and the Reynolds number: The advantage of the Ruppel number is its independence of the flow rate. Since the Ruppel number contains only fluid properties and the mass and the density of the bob, it is a constant for a particular instrument.
  48. 48. Design Charts for Laminar Rotameters
  49. 49. Design Charts for Turbulent Rotameters
  50. 50. Applications • 1. Chemical injection/dosing– controls the flow rate of the fluid to be mixed (added) to the primary fluid 2. Boiler control – measures steam flow to a boiler or measure the gases that heat the boiler 3. Tank blanketing – inert gas is the “blanket” over the liquid in a tank, which prevents the liquid from giving off vapors which could ignite and then explode 4. Simple flow measurement – options such as flow switch (alarm) or continuous electronic.
  51. 51. Muhammad Mubbasher Khan ME 113126 52
  52. 52. General Principle of Calibrating Flow Measurement Instruments CALIBRATION A calibration applies a known input value to a measurement system for the purpose of observing the system output value. It establishes the relationship between the input and output values. The known value used for the calibration is called the standard. 53
  53. 53. Methodology Standards for flow measurement are based on a comparison of the quantity of fluid passed, or passing, through the flow meter with the quantity measured by the standard. Standards can be based on the measurement of mass or volume. The required mass or volume quantity can be calculated from the measured quantity from a knowledge of the fluid density at the test flow meter. 54
  54. 54. Calibration Errors • Calibration errors include those elemental errors that enter the measuring system during its calibration. Calibration errors tend to enter through three sources. • Reference value used in the calibration. • The instrument or system under calibration. • Calibration process. 55
  55. 55. Flow Meters Available in our University 1. Rota meter 2. Venturi Meter 3. Orifice meter These flow meters are already been described in former sections. 56
  56. 56. Venturi Meter 57
  57. 57. Venturi and Orifice Meter 58
  58. 58. Rotameter 59
  59. 59. Conclusion • In this project we learnt a lot about flow measurement devices and also discuss types of these devices. In which we studied that every type have its own working principle which differentiate it from other. In mechanical engineering field accurate measurement of flow rate of liquids and gases is an essential requirement for maintaining the quality of industrial processes. 60
  60. 60. 61 0 2 4 6 8 10 12 14 16 18 0 1 2 3 4 5 6 7 8 9 10 DifferentialPressure Flow Rate Flow Analysis of Orifice meter Flow analysis of Orifice meter Flow Rate Pressure Difference 6 4.47 8 5.47 10 7.42 12 9.33 14 10.67 16 12.61 18 13.89 20 15.45
  61. 61. Thank you! 62

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